This circuit was originally designed to measure capacitance with an ICL7107 but can be used with other digital modules. The circuit is from Electronics Now magazine from November 1996.
In the figure we have the way to use a low-cost digital clock chip to trigger an alarm. The...
This circuit is the traditional 555 oscillator that produces a hum in the piezoelectric...
This circuit was found in a computer publication from the 1970s. The transistors can be the BD135...